Coolant temperature sensor.

[Jhm89]

Hey all, a few weeks back I posted about a startup issue. From all my research it seems to be CTS. But I cant confirm. Truck runs fine cold, once warms it loads up, hard to start, rough idle, too much fuel to drive. The CTS in my truck snapped into two parts. Luckily it didn't damage the manifold. I attempted to put the new CTS into the port on the left cylinder head port, but the plug with a square in it rounded out, even though I have the right bits for it. So then I just took the CTS with a green wire out for my gauge, and put the 2 prong CTS there. It didn't work, so yesterday I bought a new water outlet with ports in it, and currently have the CTS there. The problem persists. Today I received the gaskets to swap manifolds with a spare, but the truck dosent have a vacuum leak, so I'm hesitant.

Is the water neck not a suitable spot for CTS because its above thermostat and dosent receive a steady flow of coolant?

If I unplug the CTS and the problem remains does this mean its not the CTS?

The truck passed the voltage drop test, and the only sensor on it that is still original is TPS.

Maybe the answer is staring right at me, I often muck up simple things. Thank you guys for all the help and insight.

TL;DR (too long, didnt read) Why does my truck run rich on warm startups?

 

[77 K20]

Have you unplugged your MAF and tried driving it? I think that year has one...

My heads a bit foggy right now. Head cold/sinus infection type thing going on.

Something about the whole closed loop/open loop type thing. When it is cold it ignored a lot of sensors. Once it warms up, it looks at them. And if they are bad, it runs like crap.

By unplugging the MAF it forces it to just got off a table (and it is quick and free). If it runs better, maybe it just needs to be cleaned. Bad O2 sensor is the other option.

Wonder what others will chime in with...

 

[Irishman999]

I dont think its an issue with the coolant temp sensor, mine went out on the big block and it would run dog ass rich when it was cold and eventually get better. Were talking so rich it was shooting raw fuel out of the tailpipe.

I would start with the 02 sensor, that could cause a rich condition. Before you go through that ******** adjust the TPS, all you need is a multimeter and a torx driver. I adjusted mine and it made a huge difference.

 

[Irishman999]

*Dont **** with the idle air control valve, dont ever mess with an exposed idle adjustment for the linkage. Its just a big waste of time unless you have a vacuum leak you are trying to eliminate.

 

[89Suburban]

Interesting, I might adjust my TPS. I just bought a new O2 sensor too. I figured after 200k miles it can't hurt.

 

[Jhm89]

Thanks for the replies everybody.

My truck dosent have a MAF , but I did warm the engine and try to unplug each sensor one at a time. The o2 sensor unplugged let the truck start fine, but it still fell on its face.